Cobalt(II,III) oxide is an inorganic compound with the formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid. As a mixed valence compound, its formula is sometimes written as CoIICoIII2O4 and sometimes as CoO•Co2O3.
Molar mass：240.80 g/mol
Melting point：895 °C (1,643 °F; 1,168 K)
Boiling point：900 °C (1,650 °F; 1,170 K) (decomposes)
Solubility in water：Insoluble
Solubility：soluble in acids and alkalis
Magnetic susceptibility (χ)：+7380·10−6 cm3/mol
Cobalt(II,III) oxide is used as a blue coloring agent for pottery enamel and glass, as an alternative to cobalt(II) oxide.
Cobalt(II,III) oxide is used as an electrode in some lithium-ion batteries, possibly in the form of cobalt oxide nanoparticles.